Method of building reenforced concrete structures



K. J. LJUNG BERG METHOD OF BUILDING REENFORCED'CONCRETE STRUCTURES Filed March 5. 1925 means Eatented Sept. 6, 1927.

siren FF! C KARL JOI-I'A'N LJUNGBERG, 0F STOCKHQLM, SWEDEN.

METHOD OF BUILDING REENFOECED CONCRETE STRUCTURES.

Application filed March 5, 1925, Serial No. 13,196, and in Sweden July 31, 1924.

This invention relates to an improved method of building concrete arch structures of the type having a metallic reenforcement consisting wholly or partially of tubes filled with concrete and surrounded by a mam concrete body.

Several methods of building concrete arches having tubular metallic reentorcement have been proposed, but generally such methods have the drawback that the iron structures will be very heavy and expensive and that rather enpensive scailoldings or other supporting means'must be used for supporting the iron structure andthe concrete until the latter has set.

The chief object of this invention is to make it possible to use a light tubular metallic reenforcement in building arches of reenforced concrete.

A Further object of the invention isto make it possible to use a light tubular metallic reenforcement in building arches of reentorced concrete.

A further object of the invention is to make it possible to dispense with the use of scafioldings or other provisional supporting luring the filling of the tubular metallic structure with concrete as well as during the moulding of the outer concrete body and inthis manner to obtain in each of the three main parts of the structure, namely tubes, concrete filling and the surrounding main concrete body, stresses which as far as possible correspond to the strength of said parts.

With these objects in view, the invention consists, chiefly, in first erecting a light arched frame-work consisting chiefly of metal tubes and'having a carrying capacity adapted to support its own weight and the weight of a concrete mass filling the tubes, then utilizing said arched frame-work as the only supporting means during the filling of the tubes, and when said concrete filling has set, finally utilizing the arched frame-work with its concrete filling as the only supporting means for moulds and concrete in moulding the main concrete body around the metallic frame-work.

In this manner I am able to build at low cost a reentorced concrete arch having a minimum of metallic reen'forcement and the said reenforcement as well as the concrete included in the tubes will be loaded in the most effective manner. The method is especially adapted for building large bridges in which the metallic tubular reenforceinents hitherto proposed would be. too heavy and expensive for practical use.

I In the accompanying drawing shown in Fig; 1 an elevation ofa portion of an arched frame-work adapted tobe used as reenforcement in an arched bridge of re-' enforced concrete and m Fig. 2 a cross-secs tional view thereof withv concrete moulded around the reenter-cement.

ihe reenforcement consists according to the present invention wholly or partly of circular iron tubes with a rather large diam eter and a rather small thickness of the walls' The total sectional area of the tubes is, however, small in comparision with the totalsectional area of the arch as is clear from Fig. In the constructional form shown in the drawing the tubes a form the booms or chords of the frame-work. arch, the diagonal and vertical rods of whichcon sist of iron plate or profile iron I). Said frame-work. arch forms a. skeleton of'small weight as compared with thefinished reenforced concrete structure and is first erected. The building of said skeleton can be per formed in several ways. When the building ground is favorable the skeleton can be built with the aid of a wood scaffold" which on account of the small weight of the iron skeleton requires essentially smaller dimensions than if it should carry thewholeconcrete structure. Another method is to build the skeleton arch on the/ground in two halves which then are raised up in their positions by means of lifting machines" and rotated about axes at their base ends'-'where;-

upon the opposite ends are connected to each other, or it-may be preferred, dependent on t the circumstances, to build up the skeleton from the base ends as is sometimes usual in erecting arched bearing constructions ofi frame-work. Also other methods of erecting the light skeleton arch can be used.

When the iron skeleton has been erected openings in the tube walls, the tube walls When serving in this operation as moulds. the concrete filling has set, the tube structure and on account thereof also the whole skeleton construction has obtained a highly I have i The tubes of said arch are increased bearing capacity. The iron skeleton can, therefore, be made very light and notwithstanding after the filling of the tubes with concrete obtain a sufiicient bearing power for the following moulding of the main concrete body. This result depends on this that the tubes filled with concrete are used'essentially as chords or girths in the arch construction, in which the stress acts as compression and that concrete included in tubes has a rather great capacity for resisting pressure.

When the concrete in the tubes has set sufliciently, casings for the moulding of the final concrete arch are set up, said casings weight and the weight of a concrete mass filling the tubes.

2. The utilizing of said metallic skeleton as only supporting means in filling the tubes with concrete.

3. The setting up of moulds and moulding the concrete body around the metallic structure by using the reenforced iron skeleton as the only supporting structure for the moulds and'the surrounding concrete.

The filling of the tubes and the moulding of the heavy main structure can accordingly be erformed without the use of expensive scai'olding. Furthermore, another result is attained. When the metallic arched frame workjhas been erected its own weight causes in the metal an initial strain which is further increased when the tubes are filled with concrete in as much as said concrete is supported only by the tubular metallic arch. When said concrete has set and the main concrete body is moulded around. the metallic frame-work the strains of the metal is still'further increased and at the same time the concrete enclosed in the tubes receives its initial strain. lVhen also the outer concrete has set and the arch is loaded the outer main concrete body receives its strain while the strains of the metal reenforcement and of the enclosed concrete are further increased. The concrete enclosed in the tubes is thus subjected to greater stresses than the surrounding concrete. As concrete included in the tubes by the action of the tubes obtains the ability to sustain even larger pressures than concrete having spiral reenforcoment the concrete included in the tubes will be utilized in a'more economical manner in comparison with the case in which the whole concrete mass in a section is moulded simultaneously in moulds carried by an independent scaffold. In the latter'case the concrete obtains even if it is reenforced by tubes or strength than when the concrete body is l'HOUlClGCl in moulds supported by an independent scaffolding, suspension ropes or the like.

lVhat I claim is:

A method of building concrete arch structures,- comprising first erecting a light arched. frame-work consisting chiefly of empty metal tubes and having in itself a carrying capacity adapted to support its own weight; filling the tubes with a reenforcing concrete mass after erecting 'the frame-work said arched unfilled framework being the only supporting means during the filling of the tubes and when said concrete filling has set, utilizing the arched frame-work with its reenforcing concrete filling as the only supporting means for molds, and molding the main concrete body in said molds around the concrete filled tubes and metallic frame-work.

In testimony whereof I have signed my name.

KARL JOI-IAN LJUNGBERG. 

